| 摘要 |
In order to determine whether a particle is a diamond, 514.5 nm laser radiation, modulated at a frequency of 10 MHz to 1 GHz, is projected onto the particle 2, and the radiation emitted by the particle 2 is collected by a wide aperture viewing system 23 with narrow band pass filtering of the diamond Stokes or anti-Stokes Raman frequency appropriate to the laser wavelength. The emitted radiation is detected by a detector 6, and an associated electronic circuit 13,14,15 detects signals modulated at the same frequency as the laser modulation frequency. In this way, only Raman radiation is detected as this has a very short rise/decay time; other luminescence forms a background which is not modulated and can be removed by for instance thresholding, or heterodyne techniques. The method can be used to sort diamond from gangue on a wide belt, without very complicated optics. |
